Tricyclic pyrimidinones

ABSTRACT

The compounds are biologically active tricyclic pyrimidines of the class of imidazo(1,2-a)pyrido(2,3-d)pyrimidine-5(10H)-ones, pyrido(2,3-d)pyrimido(1,2-a)pyrimidine-6-ones and (1,3)diazepino(1,2-a)pyrido(2,3-d)pyrimidine-7(12H)-ones, e.g., 10-(4&#39;&#39;-fluorobenzyl)-2,3-dihydro imidazo(2,1-a)pyrido(2,3d)pyrimidine-5(10H)-one, and useful, for example, as bronchodilator agents. Processes for preparation of said compounds include the reaction of a 3,4-dihydro-1,3-dioxo-1H-pyrido(2,3d)(1,3)oxazine (a 3-azaisatoic anhydride) with a cyclic pseudothiourea such as 2-organomercapto-4,5-dihydroimidazole or 2-organomercapto-3,4,5,6-tetrahydropyrimidine.

United States Patent [1 1 Hardtmann [451 Jan. 7, 1975 1 TRICYCLIC PYRIMIDINONES [76] Inventor: Goetz E. Hardtmann, 208

Brooklake Rd., Florham Park, NJ. 07932 [22] Filed: Jan. 26, 1973 [21] Appl. No: 326,850

[52] U.S. Cl 260/256.4 F, 260/239 BC,

260/244 A, 260/251 R, 260/309.6, 424/251 [51] Int. Cl C07d 51/46 [58] Field of Search 260/256.4 F

[56] References Cited UNITED STATES PATENTS 3,598,823 8/1971 Hardtmann 260/2564 Primary ExaminerRaymond V. Rush Attorney, Agent, or Firm-Gerald D. Sharkin 1571 ABSTRACT The compounds are biologically active tricyclic pyrimidines of the class of imidazo[l,2-a]pyrido[2,3- d]pyrimidine-5( l0H)-ones, pyrido[2,3- d]pyrimido[ l ,2-a1pyrimidine-6-ones and 1,3]diazepin0[1,2-a]pyrido[2,3-d]pyrimidine-7(l2H)-ones, e.g., 10-(4-fluorobenzyl)-2,3-dihydro imidazo[2,1- a]pyrido[2,3-d]pyrimidine-5(l0H)-one, and useful, for example, as broncho-dilator agents. Processes for preparation of said compounds include the reaction of a 3,4-dihydro-l,3-dioxo-lH-pyrido[2,3-d][1,3]oxazine (a 3-azaisatoic anhydride) with a cyclic pseudothiourea such as 2-0rganomercapto-4,5-dihydroimidazole or 2-organomercapto-3,4,5,o-tetrahydropyrimidine.

35 Claims, N0 Drawings TRICYCLIC PYRIMIDINONES The present invention relates to heterocyclic substituted tricyclic compounds which are pyrimidinones, and to their preparation. The invention also relates to pharmaceutical methods and compositions for utilization of the compounds based on their biological activ- Fly.

The compounds of the invention may be represented by the structural formula 1:

wherein R is alkyl of one to seven carbon atoms, alkenyl of three to eight carbon atoms,

m is to 2, R is hydrogen, alkyl of one to four carbon atoms or alkoxy of one to three carbon atoms, n is 0 to 2, X is a direct bond or (CH p is 1 to 3,

each of Y and Y is, independently, hydrogen, halo of atomic weight not greater than 36, i.e., fluoro or chloro, or lower alkyl of one to three carbon atoms, or both are lower alkoxy of one to two carbon atoms, or one is hydrogen and the other bromo, trifiuoromethyl or lower alkoxy of one to two carbon atoms, each of R R R and R is hydrogen or alkyl of one to three carbon atoms provided that no more than 3 of R R R and R are alkyl, or a pharmaceutically acceptable acid addition salt thereof.

The compounds of the formula I may be prepared by a reaction in a Step A of a compound of the formula II:

| N N R1 l o II wherein R and R are as defined, with a compound of formula III:

N RS-f W lts HN tures represent the preferred solvents, particularly dioxane and toluene. The reaction is preferably carried out in the presence of a base, e.g., sodium hydroxide or sodium carbonate; and if the compound III is employed directly in acid addition salt form then it is desirable to employ an amount of base somewhat greater than the amount necessary to neutralize the acid. In general, the reaction product of formula I may be recovered from the reaction of Step A by working up by conventional procedures.

The compounds of the formula II are novel and may be prepared by reacting a compound of the formula IV:

in which R is as defined and M is hydrogen or an alkali metal, with a compound of the formula V:

in which R is as defined and X is halo, e.g., chloro or bromo.

The preparation of compounds II from compounds IV and V may be carried out at temperatures of from 0C. to C., preferably 20C. to 50C. The reaction is conveniently effected in an inert organic solvent which may be of conventional type, e.g., dimethylacetamide. The reaction is preferably effected with a compound IV in which M is an alkali metal and such compounds are prepared in a conventional manner by reacting a compound in which M is hydrogen with a strong base such as an alkali metal hydride, e.g., sodium hydride. If the compound IV in which M is hydrogen is employed the reaction is carried out in the presence of a strong base, e.g., an alkali metal alkoxide or hydroxide.

The compounds of formulae III, IV and V are either known or may be prepared from known materials by established procedures. With respect to the compounds of the formula IV (M being hydrogen) reference may be made to US. Pat. No. 3,622,573 and Beckwith et al., J. Chem. Soc. (C), 1968, 2756.

The preferred bronchodilator compounds of the invention are those having one or more of the following significances: (1) R being benzyl or substituted benzyl, particularly p-halobenzyl; (2) R equals hydrogen; and (3) n equals 0.

Also within the scope of the compounds of formula I of the invention are pharmaceutically acceptable salts not materially depreciating the pharmacological effect of the compounds. Such salts include the acid addition salts of known type, e.g., the hydrochloride, maleate and the like. The acid addition salts may be produced from the corresponding free bases by conventional procedures. Conversely, the free bases may be obtained from the salts by procedures known in the art.

The compounds of formula I ofthe invention are useful because they possess biological activity. In particular, the compounds of the formula I in which R is alkyl, alkenyl or substituted or unsubstituted benzyl, phenethyl or a-methyl-benzyl are useful as bronchodilator agents as indicated by measuring bronchial resistance on intravenous administration (0.2 5 mgs./kgs.) in the anesthetized guinea pig and according to the test of Knozett and Rossler, Arch. Exp. Path. and Pharmak. 195:71 (1940); and by observing the respiratory status on oral administration (0.5 100 mgs./kgs.) to the unanesthetized guinea pig exposed to aerosolized histamine dihydrochloride according to a modification of the method of Van Arman et al., J. Pharm. Pharmacol. Exptl. Therap. l33:9097, 1961; and in vitro by observing the effect (0.1 30 micrograms/ml.) on strips of guinea pig trachea according to the method of Constantine, J. Pharm. Pharmacol. 17: 384-385, 1960. For such use and depending upon known variables satisfactory results are obtained in general on the daily administration of from 0.6 to 100 milligrams per kilogram of body weight, preferably given in divided doses 2 to 4 times a day, or in sustained release form. For most mammals the administration of from 60 to 1,500 milligrams per day provides satisfactory results and dosage forms suitable for internal administration comprise to 950 milligrams of the compound in admixture with a solid or liquid pharmaceutical carrier or diluent.

The compounds of formula I in which R is alkyl, cycloalkyl, cycloalkylalkyl or substituted or unsubstituted phenyl are also useful as hypotensive agents as indicated by a lowering of blood pressure on intravenous administration (2-30 mg./kg.) to the anesthetized dog. For such use and depending upon known variables satisfactory results are obtained in general on daily administration of from 2 to 100 milligrams per kilogram of body weight. For most mammals the administration of from 40 to 1,000 milligrams per day provides satisfactory results and dosage forms for internal administration comprise from 10 to 500 milligrams in combination with a suitable carrier.

For the uses indicated above, the compounds may be combined with a pharmaceutically acceptable carrier, and such other conventional adjuvants as may be necessary, and administered orally or parenterally. For most uses, oral administration with carriers is preferred and may take place in such conventional forms as tablets, dispersible powders, granules, capsules, suspensions, syrups and elixirs. Such compositions may be prepared according to any method known in the art for the manufacture of pharmaceutical compositions, and such compositions may contain one or more conventional adjuvants, such as sweetening agents, flavoring agents, coloring agents and preserving agents, in order to provide an elegant and palatable preparation. Tablets may contain the active ingredient in admixture with conventional pharmaceutical excipients, e.g., inert diluents such as calcium phosphate, calcium sulphate dihydrate, lactose and talc, granulating and disintegrating agents, e.g., starch and alginic acid, polyvinyl pyrrolidone and acacia, and lubricating agents, e.g., magnesium stearate, stearic acid and tale. The tablets may be 'uncoated or coated by known techniques to delay disintegration and adsorption in the gastro-intestinal tract and thereby provide a sustained action over a longer period. Similarly, suspensions, syrups and elixirs may contain the active ingredient in admixture with any of the conventional excipients utilized for the preparation of such compositions, e.g., suspending agents (methylcellulose, tragacanth and sodium alginate), wetting agents (lecithin, polyoxyethylene stearate and polyoxyethylene sorbitan monooleate) and preservatives (cthyl-p-hydroxybenzoate). Capsules may contain the ,active ingredient alone or admixed with an inert solid Ingredients Weight (mg.)

l0-(4-fluorobenzyl)2,3-dihydro-imidazo [l,2-a]pyrido[2,3-d]pyrimidine-5( 1 OH )-one 50 Tragacanth l0 Lactose 222.5 Corn Starch 25 Talcum l5 Magnesium Stearate 2.5

A representative formulation is also a capsule for oral administration 2 to 4 times a day for prophylactic treatment of bronchial asthma and prepared by conventional capsulating techniques to contain the following ingredients:

Capsule Ingredients Weight (Mg.)

10-(4'-fluorobenzyl)-2,3-dihydro-imidazo ll,2-a]pyrido[2,3-d]pyrimidine-5( l0H)-one 50 Lactose 316 Sterotex K (a triglyc'erol ester lubricant) I0 In addition the compounds of the formula 1 which are useful as bronchodilators may be administered for such use by inhalation therapy in a conventional manner, e.g., by the use of nebulizers, Vaporizers, aerosols and the like. Compositions for use in administration by inhalation therapy may be prepared according to conventional procedures and contain the usual conventional ingredients employed in such compositions. A representative aerosol formulation prepared by conventional techniques for use with a metered value system contains the following ingredients:

[l,2 a]pyrido[2,3-d]pyrimidine-5(lOH)-one 0.4 20% Ethyl alcohol 10 40% Ascorbic acid 1 10% Freon ll 10 30% Freon 114 10 30% Freon 12 30 60% Buffer System pH control q.s.

Flavor q.s.

A representative formulation is also a capsule for oral administration 2 to 4 times a day for reducing blood pressure, e.g., treating hypertension, and prepared by conventional capsulating techniques to contain the following ingredients:

Capsule Ingredients Weight (mg.)

lO-cyclopropylmethyl-2.3-dihydro-imidazol1.2- a]pyridol 2,3-d]pyrimidine5( 10H )-one Lactose 300 The following examples show representative compounds encompassed within the scope of this invention and the manner in which such compounds are prepared. However, it is to be understood that the examples are for purposes of illustration only.

EXAMPLE 1 10-Methyl-2,3-dihydro-imidazo[1,2-a]pyrido[2,3- d]pyrimidine-5(10H)-one.

STEP A: To a solution of 7.5 g. of 3,4-dihydro-1,3- dioxo-1H-pyrid.[2,3-d][1,3]oxazine in 200 ml. of dimethylacetamide is added portionwise 2.3 g. of sodium hydride and the resulting mixture stirred at room temperature for 45 minutes. There is then added 7.0 g. of methyl iodide and the mixture stirred at room temperature for an additional 30 minutes. The resulting mixture is poured onto ice/water, extracted twice with ethyl acetate and the combined extracts washed 4 times with water, dried and evaporated to a solid which is dissolved in methylene chloride. The solution is treated by addition of diethyl ether on a steam bath to crystalline 4-methyl-3 ,4-dihydro- 1 ,3-dioxo-1H-pyrido[2,3- d][1,3]oxazine, m.p. l67169C.

STEP B: A mixture of 15.4 g. of 4-methyl-3,4-dihydro- 1,3-dioxo-lH-pyrido[2,3-d][1,3]xazine, 12.0 g. of 2-methylmercaptoimidazoline, 2 pellets of sodium hydroxide and 250 ml. of dioxane is refluxed for 2 hours. The reaction mixture is then evaporated to dryness, the residue dissolved in methylene chloride, washed with water, extracted twice with 2N hydrochloride acid solution, the combined extracts washed with methylene chloride and then made basic with ice/2N sodium hydroxide solution. Adding of seeding crystals results in a precipitate which is recovered by filtering, washed 4 times with water, dried in high vacuum, redissolved in methylene chloride and ethanol added on a steam bath to obtain 10-methyl-2,3-dihydroimidazo[ l ,2- a]pyrido[2,3-d]pyrimidine-5(10H)-one, m.p. 168l71C.

EXAMPLE 2 4 '-fluorobenzyl )-2 ,3-dihydro-imidazo[1,2- a]pyrido[2,3-d1pyrimidine-5( 10H)-one.

HgC N iii N F l U A mixture of 14.2 g. of 4-(4'-fluorobenzyl)-3,4- dihydro-l,3-dioxo-1H-pyrido[2,3-d][1,3]oxazine, 6.8 g. of 2-methylmercaptoimidazoline, 350 ml. of dioxane and 2 pellets of sodium hydroxide is refluxed for 8 hours and evaporated to dryness. The residue is dissolved in methylene chloride, washed with water, extracted twice with 2N hydrochloric acid and the combincd acid extracts washed with methylene chloride followed by treatment with charcoal and filtered. The filtrate is then made basic with ice/2N sodium hydroxide, seeding crystals added and the resulting crystalline material is washed 3 times with water, air dried, washed twice with diethyl ether, dried under high vacuum and recrystallized from methylene chloride/diether ether (1:1). The resulting crystalline materials are dissolved in chloroform and ethanol added while heating on a steam bath to obtain l0-(4-fluorobenzyl)-2,3-dihydroimidazo[ 1,2-a]pyrido[2,3-d]pyrimidine-5( 10H )-onc, m.p. 202205C.

EXAMPLE 3 Following essentially the procedures of Examples 1 and 2 the following additional compounds of the invention are prepared:

a. lO-benzyl-Z,3-dihydro-imidazo[1,2-a]pyrido[2,3-

d]pyrimidine-5( 10H )-0ne.

b. 10-cyclopropylmethyl-Z,3-dihydro-imidazo[1,2-

a]pyrido[2,3-dlpyrimidine-5(1OH)-one, m.p. 139142C.

c. 10-ethy1-2,3-dihydro-imidazo[1,2-a]pyrido[2,3-

d]pyrimidine-5(10H)-one.

d. 10-hexyl-2,3-dihydro-imidazo[ l ,2-a]pyrido[2,3-

d]pyrimidine-5(10H)-one.

e. 10-(2'-methylbenzyl)-2,3-dihydro-imidazo[1,2-

a]pyrido[2,3-d]pyrimidine-5(10H) -0ne.

f. 10-cyclohexyl-2,3-dihydro-imidazo[1,2-

a]pyrido[2,3-d]pyrimidine-5(10H)-one.

g. 10-(4'-chlorobenzyl)-2,3-dihydro-imidazo[1,2-

a]pyrido[2,3-d]pyrimidine-5(10H)-one.

h. 10-(4'-bromobenzyl)-2,3-dihydro-imidazo[1,2-

a]pyrido[2,3-d]pyrimidine-5(10H)-one.

i. 10-(3',4-difluorobenzyl)-2,3-dihydroimidazo[1,2-a]pyrido[2,3-d1pyrimidine- 5(10H)-one.

j. 10-pheny1-2,3-dihydro-imidazo[ 1,2-a]pyrido[2,3-

d]pyrimidine-5(1OH)-one.

k. 10-(3-trifluoromethylbenzyl)-2,3-dihydroimidazo[1,2-a]pyrido[2,3-d]pyrimidinel. 10-( 3 ,4-dimethoxybenzyl )-2,3-dihydroimidazo[ 1,2-a]pyrido[2,3-d]pyrimidine- 5( 10H )-one.

rn. 10-(a-methylbenzyl)-2,3-dihydro-imidazo[1,2-

a]pyrido[ 2,3-d]pyrimidine-5( l0H)-one.

. 10-(S-hexenyl)-2,3-dihydro-imidazo[1,2-

a]pyrido[2,3-d]pyrimidine-5( 10H )-one.

. 10-(2-buteny1)-2,3-dihydro-imidazo[1,2-

a]pyrido[2,3-d1pyrimidine-5(10H)-one.

p. l0-(4'-fluorobenzyl)-7-methyl-2,3-dihydroimidazo[1,2- a]pyrido[2,3-d]pyrimidine 5( l0H)-one.

q. l0-(4'-fluorobenzyl)-8-methoxy-2,3-dihydroimidazo[ 1,2- a]pyrido[2,3-d]pyrimidine-5(1OH)-one.

r. 10-(4'-fluorobenzyl)-2,2-dimethy1-2,3-dihydroimidazo[ l ,2- a]pyrido[2,3-d]pyrimidine-5(10H)-one.

s. 10-(4'-fluorobenzyl)-2-methy1-2,3-dihydroimidazo[1,2-a]pyrido[2,3-d]pyrimidine- 5(10l-1)-one.

t. l0-(4'-fluorobenzyl)-2,3-dimethyl-2,3-dihydroimidazo[1,2-a]pyrido[2,3-d]pyrimidineu. l l-(4-fluorobenzyl)-1,2,3,4-tetrahydro-2H- pyrido[2,3-d]pyrimido[ l ,2-a]pyrimidine-6-one. l1-benzyl-l ,2,3,4-tetrahydro-2H-pyrido[2,3-

d]pyrimido[ l,2-a]pyrimidine-6-one. w. 1 l-cyclopropylmethyl-l ,2,3 ,4-tetrahydro-2H- pyrido[2,3-d]pyrimido[1,2-a]pyrimidine-6-one.

x. 1l-(4-fluorobenzyl)-3-methyl-3ethyl-1,2,3 ,4-

tetrahydro-2H-pyrido[2,3-d]pyrimido[1,2- a]pyrimidine-6-one.

y. 1 1 -pheny1-1 ,2,3,4-tetrahydro-2H-pyrido[2,3-

d]pyrimido[ l ,2-a]pyrimidine-6-one. z 1 l-methyl-1,2,3,4-tetrahydro-2l-l-pyrido[2,3-

' d]pyrimido[1,2-a]pyrimidine-6-one. 2-1. 1 1-(5-hexenyl)-1,2,3 ,4-tetrahydro-2H- pyrido[2,3-d]pyrimido[ 1 ,2-a]pyrimidine-6-one.

2-2. 10(4-fluorobenzyl)-8-methyl-2,3-dihydroimidazo [1 ,2-a]pyrido[2,3-d]pyrimidine- H )-one.

tetrahydro[ l ,3 ldiazepino [1,2-a]pyrido[2,3- d]pyrimidine-7( 12H)-one.

2-4. 12-(4'-fluorobenzyl)-10-methyl-2,3,4,5-

tetrahydro[1,-

diazepino[ l ,2-a]pyrido[2,3-d1pyrimidine- 7( 12H )-one. 2-5. 12-cyclopropylmethyl-2,3,4,5-

d]pyrimidine-7(12H)-one.

z-6. 12-methyl-2,3,4,5-tetrahydro[1,3- ]diazepino[ l ,2-a]pyrido [2,3-d]pyrimidine- 7( 12H )-one.

wherein R is alkyl of one to seven carbon atoms, alkenyl of three to eight carbon atoms,

m is O to 2, R is hydrogen, alkyl of one to four carbon atoms or alkoxy of one to three carbon atoms,

n is 0 to 2, X is a direct bond or (CH p is l to 3,

each of Y and Y is, independently, hydrogen, halo of atomic weight not greater than 36, i.e., fluoro or chloro, or lower alkyl of one to three carbon atoms, or both are lower alkoxy of one to two carbon atoms, or one is hydrogen and the other bromo, trifluoromethyl, or lower alkoxy of one to two carbon atoms, each of R R R and R is hydrogen or alkyl of one to three carbon atoms provided that no more than 3 of R R R and R are alkyl, or a pharmaceutically acceptable acid addition salt thereof.

2. A compound of claim 1 in which R is and in which m is 1 or 2.

3. A compound of claim 2 in which m is 1.

4. A compound of claim 2 in which n is 0.

5. The compound of claim 4 which is l0-benzyl-2,3- dihydroimidazo[ 1,2-a]pyrido[2,3-d]pyrimidine- 5( lOH)-one.

6. A compound of claim 1 in which n is 1.

7. The compound of claim 4 which is 10-(4'- fluorobenzyl)-2,3-dihydro-imidazo[1,2-a]pyrido[2,3- d]pyrimidine-5( l0H)-one.

8. The compound of claim 4 which is 2,3-dihydro-10- benzyl-imidazo[ 1,2-a]pyrido[2,3-d]pyrimidine- 9. A compound of claim 2 in which Y is hydrogen or 4-halo and Y is hydrogen.

10. A compound of claim 2 in which Y and Y are selected from the group consisting of hydrogen and fluoro.

11. A compound of claim 9 in which Y is halo.

12. A compound of claim 10 in which Y is hydrogen and Y is fluoro.

13. A compound of claim 1 in which R is phenyl or substituted phenyl.

14. A compound of claim 1 in which R is 15. A compound of claim 14 in which m is l or 2.

16. A compound of claim 15 in which R, is hydrogen.

17. A compound of claim 15 in which m is l and n is 0.

18. A compound of claim 17 in which R is cyclopropylmethyl.

19. A compound of claim 18 in which R, is hydrogen.

20. A compound of claim 1 in which R and R are each hydrogen.

21. A compound of claim 14 in which n is 0.

22. A compound of claim 1 in which either both R and R are alkyl or both R and R are alkyl.

23. A compound of claim 22 in which R is 31. A compound of claim 22 in which R is cycloalkyl or cycloalkylalkyl.

32. A compound of claim 31 in which R is cycloalkylalkyL 33. A compound of claim 32 in which R is cyclopropylmethyl.

34. A compound of claim 22 in which R is phenyl or substituted phenyl.

35. The compound of 19 which cyclopropylmethyl-2,3-dihydro-imidazo[ 1,2- a]pyrido[2,3-d]pyrimidinc5( l0H)-onc. 

1. A COMPOUND OF THE FORMULA:
 2. A compound of claim 1 in which R is
 3. A compound of claim 2 in which m is
 1. 4. A compound of claim 2 in which n is
 0. 5. The compound of claim 4 which is 10-benzyl-2,3-dihydroimidazo(1,2-a)pyrido(2,3-d)pyrimidine-5(10H)-one.
 6. A compound of claim 1 in which n is
 1. 7. The compound of claim 4 which is 10-(4''-fluorobenzyl)-2,3-dihydro-imidazo(1,2-a)pyrido(2,3-d)pyrimidine -5(10H)-one.
 8. The compound of claim 4 which is 2,3-dihydro-10-benzyl-imidazo( 1,2-a)pyrido(2,3-d)pyrimidine-5(10H)-one.
 9. A compound of claim 2 in which Y is hydrogen or 4-halo and Y'' is hydrogen.
 10. A compound of claim 2 in which Y and Y'' are selected from the group consisting of hydrogen and fluoro.
 11. A compound of claim 9 in which Y is halo.
 12. A compound of claim 10 in which Y is hydrogen and Y'' is fluoro.
 13. A compound of claim 1 in which R is phenyl or substituted phenyl.
 14. A Compound of claim 1 in which R is
 15. A compound of claim 14 in which m is 1 or
 2. 16. A compound of claim 15 in which R1 is hydrogen.
 17. A compound of claim 15 in which m is 1 and n is
 0. 18. A compound of claim 17 in which R is cyclopropylmethyl.
 19. A compound of claim 18 in which R1 is hydrogen.
 20. A compound of claim 1 in which R3'' and R4'' are each hydrogen.
 21. A compound of claim 14 in which n is
 0. 22. A compound of claim 1 in which either both R3 and R3'' are alkyl or both R4 and R4'' are alkyl.
 23. A compound of claim 22 in which R is
 24. A compound of claim 23 in which m is
 1. 25. A compound of claim 24 in which n is
 0. 26. A compound of claim 22 in which Y is hydrogen or 4-halo and Y'' is hydrogen.
 27. A compound of claim 26 in which Y is halo.
 28. A compound of claim 23 in which Y and Y'' are selected from the group consisting of hydrogen and fluoro.
 29. A compound of claim 28 in which Y is hydrogen and Y'' is fluoro.
 30. The compound of claim 29 which is 10-(4''-fluorobenzyl)-2,2-dimethyl-2,3-dihydro-imidazo(1,2-a)pyrido(2,3 -d)pyrimidine-5(10H)-one.
 31. A compound of claim 22 in which R is cycloalkyl or cycloalkylalkyl.
 32. A compound of claim 31 in which R is cycloalkylalkyl.
 33. A compound of claim 32 in which R is cyclopropylmethyl.
 34. A compound of claim 22 in which R is phenyl or substituted phenyl.
 35. The compound of 19 which is 10-cyclopropylmethyl-2,3-dihydro-imidazo(1,2-a)pyrido(2,3-d)pyrimidine -5(10H)-one. 